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Immune cell offers clue to a mystery of malaria

By Lauran Neergaard
Associated Press / April 24, 2009
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WASHINGTON - A novel immune cell may offer an important new clue to why malaria kills some people and not others.

Australian researchers discovered a specialized cell crowding the bloodstream of severe malaria sufferers but not the less sick - a cell that seems to switch off a different immune-system attack.

The research, by immunologists at Monash University in Australia, is reported today in the journal PLoS Pathogens, published by the Public Library of Science.

Regarding the question of why malaria affects people so differently, today's report brings a clue. The immune system harbors numerous types of cells that have different jobs. So-called regulatory T cells, or T-regs, are thought to help keep the system in balance by tamping down overactive immune responses from other cells.

Monash University researchers tested 33 malaria-infected adults in Papua, Indonesia, half of whom were severely ill.

Both sets of patients harbored similar numbers of T-regs. But in the severe patients, many of those cells had changed to become extra-suppressive, thanks to a new and distinct receptor that formed on the cells' surface, reported immunologist Magdalena Plebanski, the lead researcher.

Also, the severe patients harbored more parasites - and different immune cells designed to eliminate those parasites were less active, the researchers found.